<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>dowhile画三角形</title>
</head>
<body>
    <script>
        function star(row = 5){
            let m = 0;
            do {
                let n = 0;
                do {
                    document.write("*");
                } while (++n <= m);
                document.write(`<br>`);
            } while (++m < row);
        }
        star(30);
    </script>
</body>
</html>